Re: Memory mapped registers (was Re: Cachi

[dkristol@see-my.sig (David Kristola)]

In article 1@nnrp1.deja.com, Robert Dewar <robert_dewar@my-deja.com> () writes:
>Well it is not portable, more portable means that you may
>get away with not having to rewrite it for a given port,
>but the huge danger, as apparently in this case, is that

The LWL/LWR & SWL/SWR problem was not a porting problem.
That code was original, and now sits on a tar tape in
a storage container locked in a room somewhere in building
151 (along with the hardware it ran on).  The world is
safe from that bit of code (the unchecked conversion to
a 32 bit integer, the code that generated the LWL/LWR
sequence was altered long ago).

The LWL/LWR part worked.  The SWL/SWR caused the hardware
to place bad data in an unintended register.  Even if
the memory at the address functioned in a byte addressable
way, memory outside the register would have been written.

>the potential non-portability does not get flagged. By
>using a machine code insertion, you definitely flag this
>as something that needs looking at in a port.

I shall use machine code insertions for this sort of
implementation in the future.  Thanks for pointing
out the potential problems.

Or, in other words: "Uncle!"  ;-)


--djk, keeper of arcane lore & trivial fluff
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